This invention relates to a method of improving the solubility of lecithin in water and to compositions for enhancing the utility of lecithin.
The term lecithin, in general, refers to the phospholipid or phosphatide groupd of substances which are widely distributed in nature. These are mixtures of the diglycerides of fatty acids linked to the choline ester of phosphoric acid. Commercial lecithin, derived from soybeans and containing a carrier of soybean oil, is the principal lecithin of commerce although it may also be obtained from other vegetable and animal sources, such as corn oil, safflower oil or egg yolk.
The acetone insoluble fraction of commercial soybean lecithin and of crude lecithin from other sources is a mixture of phosphatides and particularly phosphatidyl choline, phosphatidyl ethanolamine and inositol phosphatides along with glycolipids, sterol glycosides, phosphatidic acid and other polar lipids. This product, which may or may not contain a carrier of soybean oil, with its mixture of phosphatides is known in the trade as lecithin. The acetone insoluble phosphatides, substantially free of oil, may be extracted with alcohol to provide an alcohol extract which contains more phosphatidyl choline while the alcohol insoluble residue contains more phosphatidyl ethanolamine and inositol phosphatides and for the purposes of this invention lecithin and associated phosphatides substantially free of fatty oil are preferred. Lecithin is a vital constituent of all living cells where it plays a fundamental role in cell permeability and cell metabolism.
Phospholipids (more particularly choline lecithin) are reported to be an essential constituent of the natural moisturizing factor of the skin and are essential in giving the skin an attractive appearance. The phospholipids applied to the skin are at least partly resorbed by the body, as indicated by use of phospholipids tagged with radioactive iodine. Phospholipids are claimed to influence the suppleness of the skin and the elasticity of skin and hair. It softens hair, imparts sheen, improves body and reduces its electrostatic charge. It has been shown that phospholipids increase skin respiration and protects the skin against defatting by detergents. Absorption of lecithin is enhanced if the lecithin is reduced in size from large colloidal aggregates to the smaller molecular solute.
Commercial soybean lecithin, essentially free from oil, is a yellow, somewhat waxy solid that is soluble in most fat solvents and in hot fatty oils and in mineral oil lipid materials but is insoluble in water. Soaking in water will hydrate the lecithin and yield an opaque dispersion or emulsion. Its insolubility in water has limited its usefullness in skin and hair care preparations. Many products are relatively oil or fat free or contain such a low level of lipids that the amount of lecithin that can be incorporated in the product is too little to be of any significance. Prior to the present invention, lecithin has been generally used by dissolving the lecithin in the fatty or lipid portion of oil-water systems. If such systems were relatively free of the lipid materials that served as solvents for lecithin, the lecithin was included in the system as a dispersion or emulsion which was often unstable, of limited effectiveness or incompatible with other components.